Conventionally, some of image recording apparatuses such as inkjet printers or the like have a function of correcting a displacement of recording position. For example, a recording system disclosed in Japanese Patent Application Laid Open Gazette No. 2008-1053 includes a transfer device for transferring a plurality of recording units and recording media, and each of the recording units has a plurality of recording heads for ejecting inks of respective colors of CMYK. For adjusting a recording displacement between recording heads in a longitudinal direction along a direction of transfer, a plurality of horizontal bars extending in a lateral direction orthogonal to the direction of transfer are recorded in the longitudinal direction by a reference head. At the same time, a comparison head records a plurality of horizontal bars adjacent to the above horizontal bars while shifting recording timing by a unit amount. By checking a position at which the horizontal bar recorded by the reference head and the horizontal bar recorded by the comparison head coincide with each other in the longitudinal direction, the recording timing of the comparison head is adjusted.
For adjusting a recording displacement between recording heads in the lateral direction, a plurality of vertical bars arranged in the lateral direction are recorded by the reference head. The comparison head records a plurality of vertical bars below the above vertical bars while shifting recording timing by a unit amount. By checking a position at which the vertical bar recorded by the reference head and the vertical bar recorded by the comparison head coincide with each other in the lateral direction, the recording timing of the comparison head is adjusted.
Incidentally, in a case of using a so-called one-pass inkjet printer which records an image by one pass of a recording medium below a head, it is necessary to correct a difference in the density of image and a difference in the ejection timing between heads with high precision.
Therefore, in such an image recording apparatus, when some of heads are changed due to a failure of the head or the like, it is necessary to correct recording densities and ejection timing of the changed head every time when an image is recorded onto a recording medium having different surface property or thickness. As a result, a correction operation becomes complicated.